You completely took that out of the context. I wrote about it to show how risky it is to pick a random library, not to complain about the author.
> But surely, the moment you integrate the random library into your project, you assumed responsibility for it.
No, you don't. Your only responsibility is your project. If the library is broken, and the original author doesn't want to fix it, it's time to evaluate whether it's easier to remove it, replace it with something else or fix it yourself. You are not obliged to fix it yourself at all. I'm sorry to disappoint you, but the world doesn't work that way.
Were you my junior, telling this to me as your project manager, I'd demand you fix the bug. The reason is - we already gained from your decision to advance the project by including the external work, and at the moment you included it in your project you accepted responsibility for the issue. Failing to take responsibility for this code, whether you wrote it or not, would be a major distraction from the task, and thus does not reflect positively on you as a developer...